How to find a child item of qquickwidget

[JoeCFD]

A qml file is loaded into qquickwidget and can be displayed in a qwidget layout. I need to find a child item inside the qml file and use it in the code . I set object name to the item in the qml file. But qquickwidget-> findChild< QObject * > ( objectName ) returns nullptr. What is wrong?

If I have pure qml layout, there is no problem to find this item from root window.

[JoeCFD]

@JoeCFD Fixed it by using rootObject = m_quickWidget->rootObject() to find child object;
auto child_obj = rootObject-> findChild< QObject * > ( objectName ); works.
while qquickwidget-> findChild< QObject * > ( objectName ) does not work.